JPS58115868A - Manufacture of field-effect transistor - Google Patents

Abstract

PURPOSE:To improve high frequency characteristics, the dielectric strength between each electrode and leak current characteristics as well as to obtain the excellent interfacial condition of the Schottky interface of a Schottky barrier gate electrode by a method wherein the gate length of the titled transistor is sufficiently reduced and the recess thereof is fully widened. CONSTITUTION:The first aperture 7' is formed on a gate electrode forming region by removing the second insulating film 7 consisting of silicon nitride and the like by applying a plasma etching method and the like, and through the intermediary of said aperture, a solution such as a hydrofluoric acid and the like is contacted and etched to the first insulating film 6 consisting of silicon dioxide and the like, and the second aperture 6' is formed on the gate electrode forming region. Then, the etching mask consisting of a photoresist film 8 is removed, a solution and the like containing hydrogen peroxide and potassium hydroxide is contacted to and etching on the surface layer part of the semiconductor active layer 3 such as gallium arsenide and the like, and after a wide concave region 31 has been formed at the lower part of the gate electrode forming region, a metal film such as aluminum and the like is vapor-deposited on the whole surface. Said metal film is deposited only on the region corresponding to the first aperture 7', the region other than the above is left over as a cavity, and the Schottky barrier gate 9 is formed by performing a patterning.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for manufacturing a field effect transistor. In particular, the relatively wide recesses formed in the surface layer of the active layer
The present invention relates to a method of manufacturing a field effect transistor having a gate electrode formed on a metal layer.

(2) Background of the Technology In field effect transistors, particularly field effect transistors used for ultra-high frequencies of 4 GHz or higher, it is desirable that the gate length be as short as possible. This is because the transfer conductance increases. Furthermore, in the case of gate electrodes, in particular, gate electrodes, they are not formed directly on the semiconductor active layer, but rather on wide recesses dug into the surface layer of the semiconductor active layer. is desirable. This is because the dielectric strength between the source or drain electrode and the gate electrode is increased and the leakage current of the gate electrode is decreased. There, gallium arsenide (Ga
As) A field effect transistor having a recessed structure is preferable for a field effect transistor manufactured using a semiconductor having high electron mobility and suitable for high frequency applications.

(3) Prior Art and Problems Conventionally, methods generally used to construct a field effect transistor having a recessed structure are as follows.

After forming a source electrode and a drain electrode on the semiconductor active layer, an insulating film such as silicon dioxide (810,) is formed on the entire surface, and a photoresist film is further formed, and a gate electrode formation area of this photoresist film is formed. An etching mask is formed by forming an opening in the shape of a gate electrode, and using this etching mask, the above insulating film is etched to form an opening, and the opening q provided in this insulating film is etched. There is one method in which a recess is formed by etching the semiconductor active layer through the etching process, a metal film for a gate electrode is formed on the entire surface, and a gate electrode is formed using a lift-off method. Therefore, according to this conventional manufacturing method, the difference between the length of the recess that can be formed on the surface layer of the semiconductor active layer and the length of the gate and electrode formed using the lift-off method is It will be determined by the amount of side etching in the etching. Therefore, although it is necessary to make the above difference sufficiently large in order to obtain a sufficient recess effect, the recess according to the prior art,
When implementing the manufacturing method of Sumi field effect transistor,
It is difficult to make the recess sufficiently wide, and there is a drawback that it is impossible to manufacture a field effect transistor having a recessed structure with satisfactory characteristics. Furthermore, as a secondary drawback, since 7 to 7 m is used to form the sheet metal gourd gate electrode, sufficient pre-baking is difficult, and the area where the metal film for the sheet metal film for the rear gate electrode is formed is not sufficient. Not cleaned and the interface condition is poor □
In addition, the shape of the gate electrode may become irregular due to melting and deformation of the resist film in the vapor deposition process for forming the metal film for the gate electrode.

(4) Purpose of the invention The purpose of the present invention is to eliminate these drawbacks.
) The recess length can be made sufficiently long regardless of the gate length. Therefore, the gate length can be made sufficiently short and the recess can be made sufficiently wide to improve high frequency characteristics, dielectric strength between each electrode, and leakage current characteristics. And to improve! (b) production of a field effect transistor having a recessed structure, which can improve the interface condition of the cylindrical interface of the cylindrical gate electrode; and (c) improve the formation accuracy of the gate electrode. The purpose is to provide a method.

(5) Structure of the Invention The structure of the present invention is as follows:
After forming a thin layer such as
! The electrode and the drain electrode are formed, and -) dual-purpose silicon (
A first insulating film made of an insulator that is relatively easily etched, such as silicon nitride (813, ), is formed.
A second insulating film made of an insulating material that is relatively difficult to etch, such as N. An opening is formed in the formation region to form an etching mask, and (e) the above silicon nitride (81slJ4) is etched using this etching mask.
Plas! on the second insulating film made of etc. A second insulating film made of silicon nitride (813N) or the like is removed from the gate electrode formation region by applying an etching method or the like to form a first opening in the gate electrode formation region; A solution such as hydrofluoric acid is brought into contact with the first insulating film made of silicon dioxide (S10□) or the like through the opening and etched to form a second opening in the gate electrode formation region, and at this time, By side etching, the second opening is made larger than the first opening, and an eave-like protrusion is formed in the second insulating film.
The etching mask made of the above photoresist film is removed, and an aqueous solution containing hydrogen peroxide (HgO) and potassium hydroxide (KOIi) is applied to gallium arsenide (gallium arsenide) through the first and second openings. After contacting and etching the surface layer of the semiconductor active layer of ()aAs) to form a wide concave region at the bottom of the gate electrode formation region, the entire surface is covered with a metal such as alkaline crystal. depositing a film, the metal film being deposited only on a portion of the wide recessed region;
That is, the metal film is deposited only in the region that fits into the first opening, leaving the other regions as a cavity, and (2) the above-mentioned metal film is patterned to form a blank gate electrode.

The idea of the present invention is to form a double layer using materials with different chemical properties on the active layer on which source and drain electrodes are formed, and then selectively etch only the lower layer of this double layer to create a canopy shape with the upper layer. forming a protrusion, applying a non-directional etching method to the lower region of the protrusion to form a cavity, applying a non-directional etching method to the cavity to form a groove with a large area on the surface layer of the active layer; On the other hand, the electrode length of the capillary electrode formed on this recess is determined by the gap length of the eaves-like projections and can be made very short. The etching mask made of previously used photoresist is replaced with a material that can withstand high temperatures, such as silicon nitride (81, N4).
) etc., it is possible to make silibake possible, improve the cylindrical interface, and improve the precision of forming the gate electrode.

Therefore, the greatest feature of the present invention is that the above-mentioned wide recessed region is made much wider than the above-mentioned first opening, while the area where the gate electrode contacts the surface of the semiconductor active layer, that is, the gate length is shortened. There is a particular thing.

First, the present invention can be implemented in many ways depending on the material of the semiconductor active layer, the material of the first insulating film, the material of the second insulating film, etc. The combination of upper silicon dioxide (810,) and silicon nitride (
In addition to combinations with undoped silicon dioxide (810,) or phosphorus-doped silicon dioxide (81N),
A combination of P-8iO, ) and -silicon oxide (810), aluminum nitride (MlN) and polycrystalline silicon (POLY-
A 1m collar in combination with 81) has been prototyped and confirmed. The etching method used in each etching step is determined by the material of the insulating film mentioned above.
For example, plasma etching is applied as the etching method for silicon oxide and polycrystalline silicon, and for non-doped silicon dioxide and phosphorus-doped silicon dioxide, hydrofluoric acid
Furthermore, aluminum nitride can be etched by a phosphoric acid (pH: PO4) based etching method.Also, the semiconductor active layer can be manufactured using any material, but the high frequency characteristics Particularly excellent is arsenide gallium oxide (GaAs).

(6) Embodiment of the invention Hereinafter, an embodiment of the invention will be described with reference to the drawings.

As an example, an NLL gallium arsenide (Ga) Ir8 layer formed in a mesa shape on a moderately insulating gallium arsenide (Ga) substrate containing chromium (Or) etc. is used. The case of manufacturing field effect transistors will be described below. See Figure 1. Made of gallium arsenide (GaAs) which is formed on an insulating gallium arsenide (GaAs) substrate and does not contain impurities. / Formed on mesa on Cerafluor layer 2 101 Wa 13
A gold-darmanium (mu-Ge) film is deposited on a gallium arsenide (GaAs) active layer 3 containing impurities of rsWl and having a thickness of about 0.6 μm, and this is used as a source electrode 4. Turning is performed to form the shape of the drain electrode 5, and heat treatment is performed to ohmically connect the source electrode 4, the drain electrode 5, and the active layer 3.

Silicon dioxide (810
g) Form the film 6 and the silicon nitride (ALSXA) film 7 in an overlapping manner. The thickness of each is about 1 x zoooo.

For the former, the reactive substance is monosilane (81i14
) and oxygen (Os); for the latter, monosilane (81H4) and -nitrogen oxide (NO) or nitrogen (
A mixed gas with M, ) is suitable. Subsequently, a photoresist is applied to form a photoresist film $.

7 Photoresist II exposed after exposing this area using a photomask having a light-transmitting part in the area where the gate electrode and the active layer 3 are in contact with each other, see FIG.
s is removed to form an opening 8'. One side or diameter of this opening is approximately 1 μm, and there is an additional tooth 1. The silicon nitride (81N) film 7 is etched by applying a plasma etching method using the photoresist film 8 having the opening 8' as an etching mask.
is etched to form an open lower ′. The reactive gas is a mixed gas of carbon tetrafluoride (OF4) and hydrogen (Cl15).

In this step, not only the silicon nitride (81N) film but also the silicon dioxide (810,) film 6 is etched, but only vertically. Therefore, one side or diameter of the open lower ′ is 1 μms! degree.

Next, add 1 volume of hydrofluoric acid solution such as 1 volume of hydrofluoric acid (IP) and 1 volume of hydrofluoric acid (IP).
The silicon dioxide (SIO) film 7 is etched in the lateral direction by contacting the silicon dioxide (SIO) film 7 with a mixture of about 10 volumes and 211', creating a cavity in the area indicated by 6' in the figure. 6'
form. As a result, silicon nitride (stli4) I
I will remain in the form of a canopy. The length of 6' is α7
It will be about 5 μm.

Refer to FIG. 4 After removing the photoresist film 8, use hydrogen peroxide (!hot).
) and potassium hydroxide ([011) is brought into contact with the active layer 3 through the opening 8', the open lower part' and the opening 6' to form a recess 3' in the surface layer of the active layer 3.

Refer to FIG. 5. A metal of aluminum material IIIP is vacuum-deposited to a thickness of about 1 μm. The length of the bottom of the recess 3' in the source-drain direction is 1.9~LOsm
The length in the drain direction is z5 to 26 μm@degree.

Here, aluminum (mul) deposited on the active layer 3
The length of the metal layer is determined by the length of the open lower part of the silicon nitride (li!1sN4) film 7, so it is approximately 1 μm.
Therefore, a margin with a length of about α75 μm remains around it. The metal layer of ALDENKO GUTSUM (MUI) is re-nealed to a length of 2 to 3 μm to complete the rear gate electrode 9.

Through the above process, (one side or two diameters of the cut plate rear gate electrode with two sides or a diameter of about 1βm) is formed.
It will be formed on a recess of about 5 μm, (b)
Since there is no photoresist film when depositing the metal for the gate electrode, good contact is achieved, and when depositing the metal for the gate electrode, f→silicon nitride CB1N)H is formed.
functions as a mask, the dart shape can also be precisely controlled.

(7; As described in the detailed description of the invention, 0) The recess length can be made sufficiently long regardless of the gate length, and the gate length is sufficiently short.
The recess can be made sufficiently wide, and as a result, the high frequency characteristics can be improved, and the dielectric strength between the source electrode and the gate electrode or between the r-rain electrode and the gate electrode can be increased, and leakage current can be reduced. (b) A field effect transistor having a recessed structure, which can improve the interface condition of the cut interface of the barrier gate electrode during shredding and improve the formation and stacking of the e-gate shape. Can you provide manufacturing methods? Wear.

[Brief explanation of drawings]

Figures 1.2 and 3.4.5 show how to fabricate a recessed structure-type rear gate field effect transistor using a mesa-shaped arsenide gallium active layer according to an embodiment of the present invention. Figure 3 is a conceptual cross-sectional view after each main step of the method has been completed; l... Quickly insulating substrate, 2... 77 layers, 3...
・Nil arsenide gallium active layer, 4... source electrode,
5...r rain electrode, 6...first insulating layer (silicon dioxide layer), 7-...second insulating layer (silicon nitride layer), 8...7 photoresist film, 81 +m photo Opening of etching mask made of resist film, 7'...
- first opening (opening formed in CII silicon layer),
6'... Second opening (cavity formed in the silicon dioxide layer), 3... Recess X (recess formed in the active layer),
9... Shitkino 9 rear gate electrode. Figure 5

Claims (1)

[Claims] (1) In a method of manufacturing a field effect transistor, a trench gate electrode is formed in a recessed region formed in a region sandwiching a source electrode and a drain electrode formed on a semiconductor active layer, wherein the source electrode and the drain electrode, a first film and a second film having a different amount of etching with the same etching agent than the first film are stacked on the raw conductor active layer, Next, the second α film is removed from the gate electrode formation region. forming a first opening in the P gate electrode formation region;
Next! etching the first film through the first opening to form a second opening in the first film that is larger than the first opening; and forming a second opening larger than the first opening; etching the surface layer of the semiconductor active layer to form the recessed region, and forming a rear gate electrode on the etched surface in the recessed region by turning the rear metal film with a metal film deposited on the entire surface; A method for manufacturing a field effect transistor, characterized in that: